Desulfurization of hydrocarbon oils



Patented July 10, 1951 DESULFURIZATION OF HYDROCARBON OILS William I.Gilbert and William A. Home, Oakmont, Pa", assignors to Gulf Research &Development Company, Pittsburgh, Pa., a, corporation of Delaware NoDrawing. Application July 16, 1948,

Serial No. 39,175

7 Claims. (Cl. 19628) This invention relates to an improved procedurefor desulfurizing hydrocarbon oils.

Desulfurization of hydrocarbons is in many cases necessary since suchsulfur-containing materials corrode equipment in which they are refined,stored or used. It is known to desulfurize hydrocarbons by contactingvapors thereof with hydrogen and a contact agent. The contact agentabsorbs the sulfur and is periodically regenerated for reuse in theprocess. Excessive costs have been encountered due to the destruction ofthe contact during the desulfurization process. This has been due torapid powdering of the contact at the high temperatures employed or toloss of activity due to low heat stability.

This invention has for its object to provide improved procedure fordesulfurizing hydrocarbon oils and fractions thereof. Another object isto provide a desulfurization process of the type wherein sulfur isabsorbed on a contact agent followed by regeneration of the contact toremove the sulfur therefrom. Another object is to provide adesulfurization contact having a relatively low powdering rate andincreased stability to heat at the elevated temperatures employed fordesulfurization and regeneration. Another object is to provide adesulfurization contact which can be cheaply and easily prepared andwhich has a long, useful life, thus reducing the over-all cost of thedesulfurization procedure. Other objects will appear hereinafter.

These and other objects are accomplished by our invention, whichincludes contacting sulfurcontaining vapors of a hydrocarbon oil withhydrogen in the presence of a contactagent comprising a metal of theiron group or its oxide and a cracking catalyst base. We have found thatsuch a contact agent has a markedly reduced powdering rate, increasedheat stability, is easier to prepare by virtue of fewer requiredimpregnations, has a lower density, and a decreased cost in cents perpound.

In the following examples and description we have set forth several ofthe preferred embodiments of our invention but it is to be understoodthat they are given by way of illustration and not in limitationthereof.

The invention is applicable to the treatment of sulfur-containinghydrocarbon oils in general such as crude petroleum, reduced crude,topped crude, cracked gasoline distillate, straight run gasoline,naphtha, gas oil, shale oils, coal tar oils and oils from hydrogenationof coal. particular advantage for the treatment of high boilingmaterials such as total crude petroleum,

It is of' reduced crude and topped crude. By treating these high boilingmaterials several advantages are obtained. Thus the sulfur-containingmaterial is desulfurized before it has been subjected to any substantialrefining procedure and therefore corrosion of refinery equipment isconsiderably reduced. Also, the contact agent we employ has a certainamount of cracking activity so that the high boiling petroleumhydrocarbon is simultaneously desulfurized and partially cracked to amore valuable form, such as gasoline. All of the above-mentioned oilsmay be desulfurized at a temperature between about 600 and 950 F. Atemperature of about 700 to 850 F. is advantageous for the high boilinghydrocarbons whereas a temperature of 650 to 800 is preferred for thelow boiling hydrocarbons.

The cracking catalyst base acts as a carrier for the iron group metal oriron group metal oxide and it does not of itself absorb the sulfur.However, it improves the desulfurization activity and as mentioned alsoeffects a partial cracking. Any refractory material having a substantialcracking activity can be used. Examples of suitable materials aresilica-alumina cracking catalysts such as those prepared syntheticallyor by acid treatment of natural clays. Silica-zirconia, silicatitania,silica-alumina-titania synthetic cracking catalysts are well known andalso can be used as a carrier for the sulfur absorbing iron group metalor metal oxide. In order to be satisfactory the cracking catalyst baseshould have a conversion index of above about 15. A cracking catalystthat has been used in a conventional cracking operation can beadvantageously employed as a carrier for the desulfurizing metal ormetal oxide. Such partial use of the cracking catalyst not only removesany of the catalyst particles which are defective in that they break upor powder easily but it also seems to result in an enlargement of thecatalyst pores so that such partially used cracking catalyst can take upa larger amount of desulfurizing metal or metal oxide. We have found,furthermore, that all of the cracking catalyst supports have theadvantage over other porous types of supports that fewer impregnationsare required to incorporate the necessary amount of the desulfurizingiron group metal or metal oxide. This decreased number of impregnationsand calcinings of course reduces the initial cost of the contact andthus the cost per barrel of charged stock processed. Examples ofsuitable cracking catalyst bases are shown in Table I along withconversion index. This table also includes examples of non-active porousmaterials which would be less suitable as carriers for the purpose ofthe present invention since they have conversion index substantiallybelow 15.

1 Inactive portions of catalyst discarded from a Thermofor cracking unitas described in Litchfield et al. U. S. patent application Serial No.701,228, filed December 12, 1947.

Conversion index as used in the present speciflcation and in the claimsmeans the amount of gasoline formed when a standard Pennsylvania Dieselfuel oil, topped to an initial boiling point of 450 F. and cut to an endpoint of 650 F. is passed over 90 cc. of the catalyst to be tested at atemperature of 845 F., a pressure of l atmosphere, a liquid spacevelocity of 1.0 volume of charge oil/hour/volume of catalyst for athroughput of 1.0 volume of oil per volume of catalyst. The vapors arecondensed at 55 F. to obtain the synthetic" product. This product isthen distilled in a inch long column packed with inch glass balls to acut point of 370 F. The difference in weight between the syntheticproduct and the residual bottoms is the yield in grams of gasoline fromwhich the yield of gasoline as weight per cent of charge can becalculated.

While any iron group metal or metal oxide, i. e. nickel, cobalt, or ironor their oxides can be used, we prefer nickel and especially nickeloxide since these result in a much greater removal of sulfur.

The cracking catalyst base is composited with the iron group metal ormetal oxide in any desired manner so long as there is obtained a fairlyextensive iron group metal or metal oxide surface supported by thecracking catalyst base. The most convenient method of preparation is toimpregnate the cracking catalyst base with a water solution of a watersoluble salt of the iron group metal, which salt must be readilyconvertible into the metal or metal oxide. A suitable salt is, forinstance, the nitrate of nickel, iron or cobalt. After such impregnationthe material is drained, dried, and calcined at elevated temperature toform the oxide. This oxide may be reduced to the metal if it is desiredto use the metal in the desulfurization. Such reduction is accomplishedin a well known manner by contact with hydrogen at elevated temperature.The cracking catalystbase also may be impregnated by immersing in themolten salt of the iron group metal. For instance, hydrated nickelnitrate can be melted and the cracking base impregnated with this moltenmaterial, followed by calcining, as described above. The amount of irongroup metal incorporated may vary considerably and will depend upon theamount of sulfur which is contained in the petroleum hydrocarbon to bedesulfurized. A contact containing about 10 to per cent by weight ofiron group metal or metal oxide in general can be used. Amounts of about20 to 35 per cent nickel in the form of nickel or nickel oxide are quitesatisfactory for hydrocarbon oils which; are usually desulfurized.

The hydrogen is employed in amounts of about to 6000 cubic feet perbarrel of hydrocarbon in the liquid state. 100 to 1000 cubic feethydrogen per barrel of hydrocarbon is advantageous when desulfurizinglow boiling hydrocarbons and 1000 to 6000 cubic feet of hydrogen perbarrel of hydrocarbon is advantageous when desulfurizing heavyhydrocarbons such as total crude, topped crude, and reduced crude. Thepressure during the desulfurization is advantageously between about 100and 1000 pounds per square inch gauge.

The contact between the hydrogen and hydrocarbon vapors and the contactagent is conveniently brought about by passing a mixture of thehydrocarbon vapors and hydrogen over the contact agent at thetemperatures mentioned above. The space velocity, i. e., the volume ofliquid bydrocarbon charged per hour per volume of contact should ingeneral be between about 0.2 and 6.0. The space velocity isadvantageously between about 1 and 6 when treating low boilinghydrocarbons and between about 0.2 and 2.0 when treating heavyhydrocarbons. The hydrocarbon vapors may be diluted with othermaterials. This is advantageous in connectionwith the treatment of heavypetroleum hydrocarbons. For instance, steam may be employed as a diluentand may be used to vaporize the heavy hydrocarbon and maintain thevapors thereof in vapor form during passage over the contact. Diluentsalso are advantageous in certain cases when treating lower boilinghydrocarbons. Other suitable diluents are nitrogen and hydrocarbonvapors and gases such as straight run gasoline or methane.

Vapors of the hydrocarbon are passed over the contact agent with thehydrogen, all as described above, until hydrogen sulfide appears insubstantial amounts in the eiiluent gases and vapors. At this stage thereaction is terminated and the contact agent is regenerated. The pointat which such termination takes place will in general correspond toabout 50 to 60 per cent conversion, more or less, of the iron groupmetal or metal oxide into metal sulfide and we accordingly prefer toterminate the desulfurization reaction at about this stage.

The contact agent is preferably regenerated by contact with an oxygencontaining gas at elevated temperature in order to convert the irongroup metal sulfide into iron group metal oxide. A temperature ofbetween about 1000 and 1400 F. is employed. It is desirable to employ atemperature above 1000 F. since lower temperatures do not result in thecomplete removal of the iron group sulfide unless uneconomically longperiods of regeneration are used. While temperatures above 1400" F. canbe used, such temperatures should be employed only with catalysts whichare stable to such elevated temperatures. While our desulfurizationcontact agents are exceedingly stable, we prefer not to employtemperatures above 1400 F. since with repeated regenerations at suchhigh temperatures they will gradually lose their activity. Theregeneration is continued until substantially no sulfur dioxide appearsin the eilluent gases. With repeated regenerations the contactaccumulates a small amount of iron group metal sulfate, which is butvery slowly decomposed into sulfur dioxide and iron group metal oxideand the regeneration-is not necessarily carried to a stage such thatiron group metal sulfate is converted into the oxide. All that isnecessary is to remove substantially all of the iron group metal sulfideand this is evidenced by the substantial absence of sulfur dioxide inthe eflluent gases in the final stages 'of the regeneration. A pressureof to 500 pounds per square inch gauge may be used during theregeneration and, if desired, a diluent gas, such as steam, nitrogen,flue gas, or the like, may be added to the oxygen containing gas inorder to control the regeneration temperature. In the event the reducedor free metal is to be employed instead of the oxide, the regenerationincludes a final reduction step to convert the oxide into the 'metal.After regeneration the contact is again employed to remove sulfur fromsulfur containing vapors of a hydrocarbon oil as previously described.

Example 1 Four desulfurization contacts were prepared by impregnatingvarious porous carriers with nickel nitrate followed by calcining tonickel oxide. These four contact agents were employed to desulfurize aWest Texas crude oil having the properties shown in Table II. Theoperating conditions for this desulfurization are shown in Table III andthe relative resistance to powdering is given in Table IV.

TABLE II Inspection on West Texas crude oil charge stock Gravity, API34.1 Sulfur, weight percent 1.48 Viscosity, S. U. S. at 100 F 42.7Carbon Residue, weight percent 4.39 Distillation:

I. B. P., F 88 10, percent at T 219 50, percent at "F 548 90, percent at"F Gasoline, 400 F., E. P., vol. percent 33.4

TABLE III Operating conditions Charge stock "West Texas Crude OilTemperature, F 850 Pressure, p. s. i. g 500 Space velocity, volume ofoil/hr./volume of contact 1.0 Throughput, volume of oil/volume ofcontact 4.0 Hydrogen, cu. ft./bbl 2,000

TABLE IV Contact powdering Per Cent Fines at B8 Contact Support life,

lmo. 2mos. 3mos. Months Porooel, 27.6% N i0 32. 5 l. 5 ActivatedAlumina, 27.8% N i0..." 12.5 25. 0 37.0 4 Synthetic Silica-AluminaCracking Catalyst, 28.8% NiO 4. o 8.0 12. o 1:; Natural Silica-AluminaCracking Catalyst, 20.3% NiO 4.0 l3

"Porocei is activated natural alumina obtained by acid treating bauxite.The activated alumina" in Table IV is an activated synthetic alumina.

It will be noted that carriers such as activated alumina and "Porocel"had an exceedingly short half life and were quickly converted intopowders under the desulfurization conditions. It is quite evident fromthe data in Table IV that the contact agents prepared from crackingcatalysts powdered at a much slower rate than non-cracking carriers.Kieselguhr and silica gel supported nickel oxide contacts have also beentested qualitatively and found to powder much more rapidly than thecracking catalyst contacts described herein. In a fixed bed, channelingof the hydrocarbon charge through the contact bed would take place ifthe contact powdered at a rapid rate and as a consequence the contacttime would decrease and result in a decrease in desulfuriza- 'tion.

Example 2.The heat stability of a desulfurization contact comprising28.8 per cent nickel oxide on a synthetic silica-alumina crackingcatalyst was compared with a contact comprising 27.8 per cent nickeloxide on activated alumina. Both contacts were heated to elevatedtemperature (1600 F in the case of synthetic alumina-silica carrier and1400" F. in the case of the alumina carrier) and the degree ofdesulfurization activity compared before and after such heating. Thematerial desulfurized in these tests was the same West Texas crude oildescribed in Example 1 and the operating conditions, were the same asdescribed in Example 1. The results are given in It will be noted thatthe high temperature of 1600" F. had practically no effect on thedesulfurization efficiency of the cracking catalyst supported contactwhereas the non-cracking support type of contact was damaged whensubjected to even 1400 F. This is evidenced by higher sulfur content andlower gravity of the product obtained. Powdering of the syntheticsilica-alumine; cracking support on heating to 1400 F. duringregeneration is negligible whereas the activated alumina was nearlycompletely converted to powder.

It is therefore to be seen that we have provided a desulfurizationcontact which has exceedingly high stability under the destructive hightemperature conditions ordinarily employed in desulfurization andregeneration of desulfurization contacts. Not only are these contactsmore stable under desulfurization and regeneration conditions but theyalso have a lower cost than the non-cracking catalyst type supports.

The density of the contact agent prepared from cracking catalyst typesupports is generally about 45 to 50 pounds per cubic foot whereas thecontact prepared from non-cracking catalyst type supports has a. densityof about 55 to 70 pounds per cubic foot. The decreased density of ourcontact lowers the initial cost on a volume basis and the smaller weightof contact charged to the re- .actors would reduce the requiredmechanical strength of the supporting screen as well as reactor mountingbase.

To summarize the factors which contribute to the contact cost per barrelof charge are: contact life, powdering rate and initial cost of contactper pound. Assuming the initial cost of contact to be the same in allcases it may be calculated that the cracking catalyst type contact wouldcost about '75 per cent less than the better noncracking catalyst typecontacts and may be as much as 90 per cent less considering lowerinitial cost of preparation.

What we claim is: x

1. The process for desu furizing a sulfur-containing hydrocarbon oilwhich comprises treating ,vapm-s of said oil with a contact agentcomprising a member of the class consisting of metals of the iron groupand their oxides composited with a silica-alumina refractory catalyticmaterial capable of promoting, to a substantial extent, the conversionof higher boiling hydrocarbons into lower boiling hydrocarbons andhaving a conversion index of above about 15, in the presence ofhydrogen, at a temperature between about 600 and 950 F., terminatingthis treatment when a substantial amount of hydrogen sulfide appears inthe treated vapors, regenerating the contact agent at a temperatureabove about 1000 F. to remove substantially all of the sulfur therefromandemploying the regenerated contact agent to treat vapors of asulfur-containing hydrocarbon oil in the presence of hydrogen under theconditions specified above.

2. The process for desulfurizing a sulfur-containing hydrocarbon oilwhich comprises treating vapors of said oil with a contact agentcomprising a metal of the iron group composited with a silica-aluminarefractory catalytic material capable of promoting, to a substantialextent, the conversion of higher boiling hydrocarbons into lower boilinghydrocarbons and having a conversion index of above about 15, in thepresence of hydrogen, at a temperature between about 600 and 950 F.,terminating this treatment when a substantial amount of hydrogen sulfideappears in the treated vapors, passing an oxygen-containing gas over thecontact agent at a temperature between about 1000 and 1400" F. toconvert the iron group metal sulfide into iron group oxide, continuingsuch treatment until substantially no sulfur dioxide appears in theeiiluent, treating the contact with hydrogen and employing theregenerated contact agent to treat vapors of a sulfur-containinghydrocarbon oil in the presence of hydrogen under the conditionsspecified above.

3. The process for desulfurizing a sulfur-containing hydrocarbon oilwhich comprises treating vapors of said oil with a contact agentcomprising a member of the class consisting of metals of the iron groupand their oxides composited with a silica-alumina refractory catalyticmaterial previously used to promote the conversion of higher boilinghydrocarbons into lower boiling hydrocarbons, in the presence ofhydrogen, at a temperature between about 600 and 950 F., terminatingthis treatment when a substantial amount of hydrogen sulfide appears inthe treatpd vapors, regenerating the contact agent to re-- movesubstantially all of the sulfur therefrom and employing the regeneratedcontact agent to treat vapors of a sulfur-containing hydrocarbon oil inthe presence of hydrogen under the conditions specified above.

taining high boiling point petroleum oil which comprises treating vaporsof said oil with a contact agent comprising an oxide of a metal of theiron group composited with a silica-alumina refractory catalyticmaterial capable of promoting, to a substantial extent. the conversionof higher boiling hydrocarbons into lower boiling hydrocarbons andhaving a conversion index of above about 15, in the presence ofhydrogen, at a temperature between about 750 and 850 F., terminatingthis treatment when a substantial amount of hydrogen sulfide appears inthe treated vapors, passing an oxygen-containing gas over the contactagent at a temperature between about 1000 and 1400 F. to convert theiron group metal sulfide into iron group metal oxide, continuing suchtreatment until substantially no sulfur dioxide appears in the efiiuentand employing the regenerated contact agent to treat vapors of asulfurcontaining high boiling point petroleum oil in the presence ofhydrogen under the conditions specified above.

5. The process for desulfurizing a sulfur-containing petroleum oilselected from the group consisting of crude, reduced crude and toppedcrude which comprises treating vapors of said oil with a contact agentcomprising nickel oxide composited with a silica-alumina refractorycatalytic material capable of promoting, to a substantial extent, theconversion of higher boiling hydrocarbons into lower boilinghydrocarbons and having a conversion index above 15, in the presence ofhydrogen, at a temperature between about 750 and 850 F., terminatingthis treatment when a substantial amount of hydrogen sulfide appears insubstantial amounts in the treated vapors, passing an oxygen-containinggas over the contact agent at a temperature between about 1000 and 1400"F. to convert the nickel sulfide into nickel oxide, continuing suchtreatment until substantially no sulfur dioxide appears in the efiluentand employing the regenerated contact agent to treat vapors of asulfur-containing high boiling point petroleum oil in the presence ofhydrogen under the conditions specified above.

6. The process for desulfurizing a sulfur-containing petroleum oilselected from the group consisting of crude, reduced crude and toppedcrude which comprises treating vapors of said 011 with a contact agentcomprising nickel oxide composited with a silica-alumina refractorycatalytic material capable of promoting, to a substantial extent, theconversion of higher boiling hydrocarbons into lower boilinghydrocarbons and having a conversion index above 15, in the presence ofhydrogen, at a temperature between about 750 and 850 F., terminatingthis treatment when about 50 to 60 per cent of the nickel oxide has beenconverted into nickel sulfide, passing an oxygen-containing gas over thecontact agent at a temperature between about 1000 and 1400 F. to convertthe nickel sulfide into nickel oxide by combustion, continuing suchtreatment until substantially no sulfur dioxide appears in thecombustion gases and employing the regenerated contact agent to treatvapors of a sulfurcontaining high boiling point petroleum oil in thepresence of hydrogen under the conditions specified above.

7. The process for desulfurizing a sulfur-containing petroleum oilselected from the group consisting of crude, reduced crude and toppedcrude which comprises treating vapors of said oil with a contact agentcomprising nickel oxide com- 4. The process for desulfurizing asulfur-conposited with a silica-alumina refractory catalytic materialcapable of promoting, to a, substantial extent, the conversion of higherboiling hydrocarbons into lower boiling hydrocarbons and having aconversion index above 15, in the presence of hydrogen, at a temperaturebetween about 750 and 850 F., at a space velocity of between about 0.2and 2.0, at. a pressure of between about 100 and 1000 p. s. i. g. and ahydrogen to oil ratio of between about 1000 and 6000 cubic feet perbarrel, terminating this treatment when a substantial amount of hydrogensulfide appears in the treated vapors, passing an oxygen-containing gasover the contact agent at a temperature between about 1000 and 1400 F.to convert the nickel sulfide into nickel oxide by combustion,continuing such treatment until substantially no sulfur dioxide appearsin the combustion gases and employing the regenerated contact agent totreat vapors of a sulfur-containing high boiling point petroleum oil inthe presence of hydrogen under the conditions specified above.

WILLIAM I. GILBERT. WILLIAM A. HORNE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. THE PROCESS FOR DESULFURIZING A SULFUR-CONTAINING HYDROCARBON OILWHICH COMPRISES TREATING VAPORS OF SAID OIL WITH A CONTACT AGENTCOMPRISING A MEMBER OF THE CLASS CONSISTING OPF METALS OF THE IRON GROUPAND THEIR OXIDES COMPOSITED WITH A SILICA-ALUMINA REFRACTORY CATALYTICMATERIAL CAPABLE OF PROMOTING, TO A SUBSTANTIAL EXTENT, THE CONVERSIONOF HIGHER BOILING HYDROCARBONS INTO LOWER BOILING HYDROCARBONS ANDHAVING A CONVERSION INDEX OF ABOVE ABOUT 15, IN THE PRESENCE OF HYDROGENAT A TEMPERATURE BETWEEN ABOUT 600* AND 950* F., TERMINATING THISTREATMENT WHEN A SUBSTANTIAL AMOUNT OF HYDROGEN SULFIDE APPEARS IN THETREATED VAPORS, REGENERATING THE CONTACT AGENT AT A TEMPERATURE ABOVEABOUT 1000* F. TO REMOVE SUBSTANTIALLY ALL OF THE SULFUR THEREFROM ANDEMPLOYING THE REGENERATED CONTACT AGENT TO TREAT VAPORS OF ASULFUR-CONTAINING HYDROCARBON OIL IN THE PRESENCE OF HYDROGEN UNDER THECONDITIONS SPECIFIED ABOVE.